Instrument for use in surgery

ABSTRACT

An instrument for use in surgery includes a hollow shaft connectable to a drive shaft of a bone anchor insertion device in a rotationally fixed manner, a needle holder configured to hold a needle and movable axially relative to the hollow shaft, an actuator rotatable relative to the hollow shaft, and a transmission member connectable to the needle holder and movable axially relative to the actuator. The transmission member is positionable around at least part of the hollow shaft and includes a first advancement surface engageable with a second advancement surface of the hollow shaft to convert a rotational movement of the actuator into axial movement of the needle holder relative to the hollow shaft for axially advancing and retracting the needle held by the needle holder.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to and the benefit of U.S.Provisional Patent Application No. 63/280,765, filed Nov. 18, 2021, thecontents of which are hereby incorporated by reference in theirentirety, and claims priority from European Patent Application EP 21 208986.6, filed Nov. 18, 2021, the contents of which are herebyincorporated by reference in their entirety.

BACKGROUND Field

The application relates to an instrument for use in surgery, inparticular, in connection with a bone anchor insertion device. With theinstrument, a position of a needle relative to the bone anchor can beadjusted. Further, the invention relates to a surgical instrumentincluding the bone anchor insertion device and the aforementionedinstrument. The surgical instrument may in particular be used inmusculoskeletal surgery, and more particularly in spinal surgery.

Description of Related Art

In surgery of the spine, a known technique involves the use of Jamshidineedles for inserting Kirschner wires (K-wires), which may be used forthe placement of bone anchors such as pedicle screws. According to theknown method, first, a small incision is made in the skin of thepatient. After that, a Jamshidi needle including a tiny awl is advancedthrough the incision to the bone. A bore is prepared by hammering andturning the Jamshidi needle back and forth and then the awl is removed.Subsequently, a K-wire is placed into the hole and the Jamshidi needleis removed. A thread cutter is guided by the K-wire to the hole, and athread is cut with the thread cutter. After cutting the thread, thethread cutter is screwed back. Finally, a cannulated bone screw isguided by the K-wire to, and screwed into, the threaded hole. As a laststep, the K-wire is removed. In total, these steps require the use ofseveral instruments and several instrument passes and may be timeconsuming, especially in cases where many threaded bores have to beprepared.

A bone anchor insertion device for holding and inserting a bone anchorinto the bone, in particular for use with a pedicle screw, is known, forexample, from U.S. Pat. No. 10,105,165 B2. The bone anchor insertiondevice includes a holding member with a seat for holding the head of thebone anchor, the holding member having two arms that are configured toencompass the head of the bone anchor, and a drive shaft for engagingthe head of the bone anchor to screw the bone anchor into bone, and adisplacement member acting onto the holding member such that the holdingmember can assume a first configuration in which the head can enter theseat and a second configuration in which the head is held in the seatand the shank of the bone anchor can be screwed into bone.

U.S. Pat. No. 10,433,883 B2 describes surgical instruments fordelivering bone anchor assemblies into bone. Use of these assemblies caneliminate one or more of the steps in a conventional bone anchorinstallation procedure. The surgical instrument includes a handleassembly having an elongate shaft extending distally therefrom. Thehandle assembly can be configured to axially translate a carrierassembly that secures a stylet extending therethrough. Translation ofthe stylet can be made relative to a distal end of the elongate shaft.

SUMMARY

It is an object of the invention to provide an improved instrument thatallows a number of surgical steps to be reduced and that makes certainsurgical steps more efficient.

According to a first aspect of the invention, an instrument for use insurgery, in particular, in connection with a bone anchor insertiondevice, includes a hollow shaft configured to connect to the drive shaftof a bone anchor insertion device, a needle holder configured to receivea needle and to be translated with respect to the hollow shaft, anactuator rotatable with respect to the hollow shaft, and a transmissionmember configured to be coupled to the needle holder and to convert arotational movement of the actuator to a translational movement of theneedle holder to advance and retract the needle. The transmission memberhas a first advancement structure that is configured to engage a secondadvancement structure provided at the hollow shaft for effecting thetranslational movement of the needle holder.

The term needle as used herein includes any elongate member that mayextend through a cannulated shank of a bone anchor such as, for example,a Jamshidi needle, an awl, a stylet, a needle of a syringe, and others.

With the instrument, the needle can remain at a fixed position duringinsertion of the shank of the bone anchor in bone. A needle of a fixedlength may be used together with bone anchors with different shanklengths. The length of the shank of the bone anchor used with theinstrument can be set on a first scale and displayed on the instrument.Moreover, the length of the needle portion that protrudes out of the tipof the shank can be adjusted and displayed on a second scale on theinstrument. Hence, an adjustment of the needle position can be carriedout easily and safely.

The position of the tip of the needle in the axial direction relative tothe tip of the bone anchor can be adjusted in a stepless manner orincrementally. The travel path of the needle may be around 50 mm to 70mm. Once a position of the needle has been adjusted, this position canbe maintained and the shank of the bone anchor can be screwed into thebone. Removal and/or exchange of the needle, if necessary, can becarried out in a simple and time efficient manner. It may also bepossible to use the instrument with needles of different type and/orwith needles of different length.

The instrument is compact. A cavity formed in the handle portion thatdrives the drive shaft of the shank inserter is used for housing theneedle advancement mechanism and defines a path of translation of theneedle holder.

The instrument may be coupled to any bone insertion device, which alsomay be called a shank inserter, and which includes a drive shaft toengage and rotate a bone anchor with a threaded shank into bone. Such ashank inserter may have a standard coupling at the rear end of the driveshaft, for example, a ¼ inch square connection portion, that can becoupled to the instrument via a standard coupling used for ¼ inchconnection portions. Hence, the instrument can form a part of a modularsystem and can preferably be selectively coupled to different shankinserters. Moreover, the instrument may be used together with an adaptercarrying a navigation instrument for computer aided imaging and/ornavigation or robotics.

With the instrument according to embodiments of the invention, varioustechniques for anchoring a bone anchor in bone may be realized. Inparticular the instrument may be used in minimally invasive surgery(MIS), and preferably using bone anchors with a self-cutting thread.

An embodiment of a method of use includes at least the steps ofconnecting the instrument to a drive shaft of another instrument forinserting a bone anchor into bone before or after connecting acannulated bone anchor to the drive shaft, inserting a needle into theinstrument and fixing the needle, translating the needle via theactuator such that a tip of the needle extends out of the tip of thebone anchor to a desired distance, inserting the needle into bone,preferably further translating the needle relative to the bone anchor toa desired depth, and inserting the bone anchor along the needle byrotating the handle portion. Afterwards, the needle may be removed fromthe bone anchor before removing the shank inserter with the instrument,or simultaneously therewith. The method may further include a step ofsetting the shank length of the bone anchor used on a first scale andadjusting the length of the needle that protrudes out of the bone anchoron a second scale.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will become apparentfrom the description of embodiments by means of the accompanyingdrawings. In the drawings:

FIG. 1 shows a perspective exploded view of an embodiment of theinstrument, a shank inserter, and a bone anchor attached to the shankinserter.

FIG. 2 shows a perspective view of the instrument and the shank inserterof FIG. 1 in an assembled state.

FIG. 3 shows a perspective view of the instrument and the shank inserterof FIGS. 1 and 2 with the bone anchor, prior to insertion of the boneanchor in a vertebra.

FIG. 4 shows a perspective exploded view of the instrument shown inFIGS. 1 to 3 .

FIG. 5 shows a perspective view of the instrument of FIG. 4 in anassembled state.

FIG. 6 shows a cross-sectional view of the instrument of FIGS. 4 and 5 ,with a needle inserted therein, the cross-section taken in a planeincluding an axis of rotation of a handle portion and an actuator of theinstrument, wherein a needle holder is in an intermediate position.

FIG. 7 shows a cross-sectional view of the instrument of FIGS. 4 to 6without the needle, and wherein the needle holder is in a retracted orrearmost position.

FIG. 8 shows a cross-sectional view of the instrument of FIGS. 4 to 7 ,wherein the needle holder is in an advanced or foremost position.

FIG. 9 shows a perspective view from a front end of a hollow shaft thatis part of the instrument of FIGS. 4 to 8 .

FIG. 10 shows a perspective view from a rear end of the hollow shaft ofFIG. 9 .

FIG. 11 shows a cross-sectional view of the hollow shaft of FIGS. 9 and10 , the cross-section taken in a plane including a central longitudinalaxis of the hollow shaft.

FIG. 12 shows an enlarged perspective view from a rear end of a needleto be used with the instrument of FIGS. 4 to 8 .

FIG. 13 shows a perspective exploded view of the needle holder of theinstrument of FIGS. 4 to 8 .

FIG. 14 shows a perspective exploded view of the actuator of theinstrument of FIGS. 4 to 8 for actuating the movement of the needleholder.

FIG. 15 shows a perspective exploded view of a transmission member ofthe instrument of FIGS. 4 to 8 for transmitting the movement of theactuator to the needle holder, and of a needle position indicationdevice in the form of a ring.

FIG. 16 shows a perspective view from a front end of the handle portionof the instrument of FIGS. 4 to 8 .

FIG. 17 shows a perspective view from a rear end of the handle portionof FIG. 16 .

FIG. 18 shows a rear view of the handle portion of FIGS. 16 and 17 .

FIG. 19 shows a cross-sectional view of the handle portion of FIGS. 16to 18 , the cross-section taken in a plane including an axis of rotationof the handle portion.

FIG. 20 shows a perspective view from a top of a shank length and needleposition indication device of the instrument of FIGS. 14 to 18 .

FIG. 21 shows a perspective view from a bottom of the shank length andneedle position indication device of FIG. 20 .

FIG. 22 shows another perspective view from the top of the shank lengthand needle position indication device of FIGS. 20 and 21 .

FIGS. 23 a to 23 d show schematic views of steps for using theinstrument together with a shank inserter, a bone anchor, and a needle.

FIG. 24 shows a perspective view of a second embodiment of a surgicalinstrument which includes the instrument of FIGS. 1 to 23 d.

FIG. 25 shows a perspective exploded view of another embodiment of aneedle holder and a needle.

FIG. 26 shows a perspective view of the needle holder and the needle ofFIG. 25 in an assembled state.

FIG. 27 shows a cross sectional view of the needle holder and the needleof FIGS. 25 and 26 , with the needle inserted in the needle holder, thecross-section taken in a plane including a longitudinal axis of theneedle.

DETAILED DESCRIPTION

Referring to FIGS. 1 to 3 , an instrument 100 is configured to be usedwith a surgical instrument, such as a shank inserter 10, that is adaptedto insert a bone anchor 1 into bone. The bone anchor 1 usually has athreaded shank 2 with a tip 3 and may also have a head (not shown) atthe end of the shank 2 opposite the tip 3. For example, the bone anchormay be part of a polyaxial bone anchoring device, wherein the head ofthe bone anchor is held in a receiving part 1 a. A needle 4 may be usedto place the bone anchor 1 at the desired position on the bone surfaceand to prepare a tiny hole in the bone that defines the insertion pathfor the bone anchor 1. For this purpose, the bone anchor 1 may becannulated so that the needle 4 can extend through the bone anchor 1from the head to the tip 3. The shank inserter 10 may be any known boneanchor insertion device. Such a shank inserter 10 is configured toengage the bone anchor 1, usually at the head, with a front end of adrive shaft (not shown in detail), so that torque can be transmitted viathe drive shaft to the shank 2 to screw the shank 2 into the bone. Thedrive shaft may have a connection portion, for example, with a polygonouter contour or a square end such as a ¼ inch connection, at its rearend that is shaped and sized to permit quick connection to and releasefrom other instrument parts, such as a T-handle 11 or another type ofhandle or adapters. A gripping portion 12, such as a thickened portionwith axial grooves, may also be provided for the shank inserter 10. Toallow the use of the needle 4, the drive shaft is cannulated. Thispermits the needle 4 to extend completely through the drive shaft andthrough the bone anchor 1. It shall be noted that the shank inserter mayalso include only a drive shaft, without other holding or counterholding features that engage the bone anchor.

Referring further to FIGS. 4 to 6 , the instrument 100 can be coupledvia a coupling portion 15 to the shank inserter 10, and morespecifically, to the drive shaft of the shank inserter 10. The couplingportion may optionally be part of the instrument. The instrument 100includes a hollow shaft 20 that is configured to be connected via thecoupling portion 15 to the drive shaft of the shank inserter 10, andthat is further configured to be connected to a handle portion 30. Thehandle portion 30 can be rotated by a user, whereby the torque istransmitted to the hollow shaft 20 and the drive shaft of the shankinserter 10. A fixation member 40 may be used to connect the hollowshaft 20 with the handle portion 30 in a rotationally andtranslationally fixed manner. Moreover, the hollow shaft 20 is housed atleast partially in a cavity of the handle portion 30. A needle holder 50is adapted to be arranged in the hollow shaft 20. The needle holder 50can be translated within the hollow shaft 20 via an actuating mechanismto permit a tip 6 of the needle 4 to be advanced and retracted relativeto the tip 3 of the shank 2 of the bone anchor 1.

The actuating mechanism includes an actuator 60 and a transmissionmember 70. The actuator 60 is rotatable relative to the hollow shaft 20and the drive shaft of the shank inserter 10. The transmission member 70is guided by the actuator 60 in a manner such that when the actuator 60is rotated, the transmission member 70 follows the rotational movementof the actuator and, at the same time, advances axially relative to thehollow shaft 20. In addition, the transmission member 70 is connected tothe needle holder 50 in a manner such that the needle holder 50 followsthe axial advancement of the transmission member 70. Thus, thetransmission member 70 is configured to convert a rotational movement ofthe actuator 60 into a translational movement of the needle holder 50.By means of this, the needle 4 can be advanced and retracted relative tothe bone anchor 1 independently from a position of the bone anchor 1. Anaxis of rotation R of the instrument 100, which is also a centrallongitudinal axis of the instrument, is coaxial with the axis ofrotation of the shank inserter 10 and the screw axis of the bone anchor1.

The parts of the instrument 100 will now be explained in greater detail.Referring additionally to FIGS. 9 to 11 , the hollow shaft 20 is anelongate, substantially cylindrical part which has a front end 20 a anda rear end 20 b. The front end 20 a faces towards the shank inserter 10when the instrument is mounted to the shank inserter. Moreover, thehollow shaft 20 defines a channel extending through the hollow shaftfrom the front end to the rear end, such that the needle 4 can extendfully therethrough. The channel has various sections describedhereinafter. Adjacent to the front end 20 a, there is a connectionportion 21 for connecting the hollow shaft 20 to the coupling portion15. The connection portion includes, at the front end 20 a, a hollowcylindrical section 21 a with an outer diameter such that thecylindrical section 21 a is configured to be received in the couplingportion 15, and with an inner diameter sized to receive a portion of thedrive shaft. Adjacent to the cylindrical section 21 a, there is asection 21 b with a greater outer diameter so that a step 21 c is formedtherebetween. The step 21 c may serve as an abutment for a spring of theconnection portion 15 (see FIGS. 6 to 8 ). Another abutment for an endsurface of the coupling portion 15 may be formed by a small outwardlyextending annular protrusion 21 d adjacent to the front end 20 a. Thesection 21 b has, close to the step 21 c, several equidistantlydistributed circumferential compartments 22 for engagement members, suchas balls 18, that are configured to engage a groove of the drive shaftto hold an axial position of the drive shaft while allowing rotation ofthe drive shaft. At a side of the compartments 22 positioned closer tothe rear end 20 b, a receiving section 23 for receiving the connectionportion of the drive shaft is formed, that has an inner contour matchingthe outer contour of the connection section, to provide a form-fitconnection between the drive shaft and the hollow shaft 20. Preferably,the receiving section 23 has a standard connection contour, such as aquarter inch female square contour. At a distance from the step 21 c, acircumferential flange or annular projection 24 may be provided that isconfigured to cooperate with a portion of the actuator 60. A pluralityof axial grooves 24 a are equidistantly formed in the outer surface ofthe projection 24, which are adapted to be engaged by balls of theactuator 60. Adjacent to the receiving section 23 towards the rear end20 b, a narrowed section 25 of the channel may have a width that is onlyslightly greater than an outer diameter of the needle 4. This mayprovide guidance for the needle 4 once the needle extends through thehollow shaft 20.

The channel then widens towards the rear end 20 b into a needle holderreceiving section 26, which serves for receiving the needle holder 50therein. The needle holder receiving section 26 has a length such thatthe needle holder 50 can move therein in an axial direction along adefined length. At least one, preferably four, axially elongate slots 27that are closed at both ends are formed in the wall of the hollow shaft20 equidistantly in the circumferential direction. The slots 27 permitpins 73 to extend therethrough for holding the needle holder 50, asdescribed in greater detail below. When the pins 73 abut against or areclose to the rear end of the slots 27 that are located closer to therear end 20 b of the hollow shaft 20, respectively, the needle holder 50is in a rearmost position (FIG. 7 ). When the pins 73 abut against orare close to the opposite front end of the slots 27, respectively, theneedle holder 50 is at a foremost position (FIG. 8 ).

Between the annular projection 24 and a position at a distance from therear end 20 b, the outer surface of the hollow shaft 20 includes anadvancement structure, which in this embodiment is a thread 200. Thethread 200 is configured to cooperate with an advancement structureprovided on the transmission member 70 to facilitate an axialadvancement of the transmission member 70 along the outer surface of thehollow shaft 20. The outer diameter of this threaded section of thehollow shaft 20 may be smaller than that of the annular projection 24.The type of thread depends on the application and the desired dependencybetween the action of the actuator 60 and the advancement of the needleholder 50. Thus, the pitch, the threadform, and the number of threadentries may be selected accordingly. A multiple thread may be used forobtaining a greater advancement of the needle. In the embodiment, athread with three entries is used. However, a single thread, a doublethread, or any other multiple thread may also be applied.

Adjacent to the rear end 20 b, a reduced outer diameter section 28 withan external thread is formed that is configured to cooperate with aninternal thread in a bore of the fixation member 40 (FIGS. 4 and 6 to 8). In addition, a plurality, more specifically four, axial slots 29extend through the end portion with the outer thread. Thereby, posts 280are formed that are configured to extend through corresponding recessesin the handle portion 30 to provide a form-fit connection between thehollow shaft 20 and the handle portion 30. In this manner, rotation ofthe hollow shaft 20 relative to the handle portion 30 is prevented whenthe fixation member 40 is screwed onto the posts 280 of the hollow shaft20. It shall be noted that other rotation preventing structures betweenthe hollow shaft 20 and the handle portion 30 may also be envisaged.

In the following, the coupling portion 15 which couples the hollow shaft20 to the drive shaft will be described in greater detail. The couplingportion 15 is exemplary and any outer suitable coupling can also beused. As best seen in FIGS. 4 to 8 , the coupling portion 15 is asleeve-like part and is configured to receive a portion of the hollowshaft 20 therein. The coupling portion 15 has a front section 16adjacent to a front end 15 a and a rear section 17 adjacent to a rearend 15 b. The rear section 17 has an inner diameter such that the rearsection fits tightly around the lager diameter section 21 b of thehollow shaft and an outer diameter that allows the rear section 17 toprotrude into a portion of the actuator 60. The front section 16 extendsaround the cylindrical section 21 a of the hollow shaft 20. Moreover,the front section 16 is flexible, for example, by means of axial slits16 a, as best seen in FIG. 5 , that are open to the front end 15 a. Theslits 16 a and an inner annular projection 16 b at the front end enablethe front section 16 of the coupling portion 15 to be snapped over theportion 21 a of the hollow shaft 20 and to abut against the annularprojection 21 d adjacent to the front end 20 a of the hollow shaft 20.In the front section 16, a compartment is formed in which a helicalspring 19 is accommodated. The helical spring 19 extends around theportion 21 a of the hollow shaft 20 and abuts against the step 21 c. Bymeans of this, the hollow shaft 20 is biased against the annularprojection 16 b of the coupling portion 15, so that the two parts arefirmly connected. At a distance from the front end 15 a, the balls 18are placed into the compartments 22 of the hollow shaft 20 and extendradially inwardly to some extent to permit rotation of the hollow shaft20.

Referring to FIGS. 12 and 13 , the needle 4 and the needle holder 50will now be described in greater detail. As depicted in FIG. 12 , theneedle 4 includes a thin rod portion 5 with a tip 6 at its front end.The tip 6 preferably is a sharp tip that is suitable for forming a holein bone. At the side opposite to the tip 6, a holding portion isprovided that includes a cylindrical front portion 7, an intermediatethicker portion 8, and a head portion 9 at a rear end 4 b. Preferably,the rod portion 5 and the holding portion are separate parts. A rear end5 b (FIG. 6 ) of the rod portion 5 may be mounted to the cylindricalfront portion 7 of the holding portion, for example, press-fit into abore of the cylindrical front portion 7, so that between the rod portion5 and the cylindrical front portion 7, a small shoulder 7 a is formed.At the outer surface of the intermediate portion 8, two projections 8 a,preferably cylindrical projections, extend outward in oppositedirections. The projections 8 a serve for mounting the needle 4 to theneedle holder 50. The head portion 9 has an engagement portion 9 a for atool at its free end. With the tool, such as a driver, the needle 4 canbe pushed and rotated to mount and release the needle from the needleholder 50. It shall be noted that the needle can be any suitable needle,such as a Jamshidi needle or a needle having a special tip, such as atip provided with a sensor.

As shown in FIGS. 6 to 8 and 13 , The needle holder 50 is asubstantially cylindrical part with a front end 50 a and a rear end 50b. The needle holder defines a channel extending completely through theneedle holder from the front end 50 a to the rear end 50 b, such thatthe tip 6 of the needle 4 can be inserted from the rear end 50 b and canextend with the rod portion 5 all the way through the needle holder 50.Adjacent to the front end 50 a, the channel has a front section 51 withan inner diameter large enough to guide the rod portion 5 of the needle4 therethrough and to further house a biasing member for holding theneedle in the needle holder. At a distance from the front end 50 a, fourthreaded radially extending through holes 52 are formed equidistantly inthe circumferential direction in the wall of the needle holder 50. Thethrough holes 52 are configured to receive the connection pins 73 (seealso FIGS. 4 and 6 to 8 ) therein to connect the transmission member 70to the needle holder 50. Each connection pin 73 has a threaded frontportion 73 a that is configured to engage a corresponding one of thethreaded holes 52 in the needle holder 50. Opposite to the front portion73 a, the connection pins 73 have a rear end 73 b with an engagementstructure, such as a slit or a polygonal recess, for screwing in thepin. The threaded front portion 73 a has a smaller outer diameter thanthe remaining pin, and a length such that the connection pin 73 can beinserted into the needle holder 50 only to a depth such that the needle4 inside the needle holder is not touched by the connection pins 73. Tolimit the insertion, a counterbore 52 a at the entrance of the threadedthrough hole 52 may be provided against which a portion of the pin 73abuts. Adjacent to the rear end 50 b, a rear section 53 for theintermediate portion 8 of the needle 4 is provided. In the front portion51 of the channel, a helical spring 55 is housed between a washer 56that is fixed to the front end 50 a and configured to permit the rodportion 5 of the needle to pass therethrough and a movable washer 57against which the shoulder 7 a of the needle 4 is configured to abut.

At the rear end 50 b, two axially extending recesses 58 that are offsetby 180° from each other are formed in the wall of the needle holder 50,that permit the projections 8 a of the intermediate portion 8 of theneedle 4 to be guided therethrough when the needle 4 is inserted. At adistance from the rear end 50 b, the recesses 58 continue into endportions 59 which extend in the circumferential direction, and thus aretransverse to the axial portion of recesses 58. The end portions 59extend circumferentially in a same rotational direction, so that whenthe projections 8 a of the needle 4 reach the end portions duringinsertion of the needle, rotation in one direction moves the projectionsinto the end portions 59 of the recesses 58, respectively, and rotationin the other direction moves the projections out of the end portions.

Referring to FIGS. 14 and 4 as well as FIGS. 6 to 8 , the actuator 60will be described. The actuator 60 includes a sleeve-shaped actuatorwheel 61 that has a front end 61 a and a rear end 61 b, wherein in themounted state, the front end 61 a faces the connection portion 15. Atthe front end 61 a, a coaxial recess 62 may be formed that is configuredto receive a portion of the rear end 17 of the connection portion 15.Following the recess 62, the inner diameter of the sleeve is such thatthe annular projection 24 of the hollow shaft 20 fits therein and abutsin the axial direction against a step 62 a. Between the step 62 a andthe rear end 61 b, the inner diameter of the sleeve is such that thethreaded portion of the hollow shaft 20 can pass and extendtherethrough. In the free end surface of the rear end 61 b, a plurality,in the embodiment four, equidistantly arranged circumferentiallyextending slits 63 are formed that serve for receiving portions of anactuator tube 64 therein, for example, in a press-fit manner. The slits63 may have enlarged end portions on both ends, respectively, forfacilitating mounting of the actuator tube 64. The outer surface of theactuator wheel 61 includes a gripping structure 65 which may includeaxially extending depressions or grooves that facilitate gripping androtating the actuator wheel 61.

The actuator tube 64 has a front end 64 a and a rear end 64 b, and aplurality of axially extending slits 66, in the embodiment four slits.The slits 66 are open towards the front end 64 a and closed towards therear end 64 b, so that four tube sections 67 are formed. The tubesections 67 are mounted with the front end 64 a into the recesses 63 ofthe actuator wheel 61. Thereby, the actuator tube 64 protrudes from therear end 61 b of the actuator wheel 61, with a smaller diameter comparedto that of the actuator wheel. The length of the actuator tube 64 issuch that in the mounted state, the rear end 64 b of the actuator tubeextends up to a small distance from the rear wall of the handle portion30. When the actuator is mounted to the hollow shaft 20, the mountingpins 75 that connect the ring 76 with the transmission member 70 canextend through the slits 66, respectively.

The actuator 60 may be mounted to the hollow shaft 20 via a springbiased rotatable connection. As shown in particular in FIGS. 4 and 6 ,at an axial position corresponding to the position of the annularprotrusion 24 of the hollow shaft 20, the actuator wheel 61 defines aplurality of equidistantly arranged threaded through holes 68, in theembodiment three through holes. Balls 69 are arranged in the throughholes 68 and are pressed via helical springs 600 by the action of setscrews 601 against the surface of the protrusion 24 of the hollow shaft20. The grooves 24 a provide resting positions that can be engaged bythe balls 69 incrementally when rotating the actuator wheel 61. In otherwords, when rotating the actuator wheel 61, the balls 69 can move out ofeach of the grooves 24 a and snap into circumferentially neighboringgrooves 24 a. Thus, a haptic feedback may be given to a user when theactuator wheel is rotated. The actuator wheel 61 is prevented from axialmovement since the actuator wheel is connected via the actuator tube 64to the transmission member 70 and the needle holder 50.

The transmission member is shown in greater detail in FIG. 15 . Thetransmission member 70 is a sleeve-like part with a front end 70 a and arear end 70 b. An internal thread 71 configured to cooperate with theexternal thread 200 on the hollow shaft 20 is formed on the inner wallof the sleeve to allow the transmission member 70 to move back and forthon the hollow shaft 20 in the axial direction. The advancement structurein the form of the thread 71 on the transmission member 70 and theadvancement structure in the form of the thread 200 on the hollow shaft20 may be configured such that the distance per revolution which thetransmission member 70 moves axially corresponds to the distance theshank 2 is advanced per revolution of the drive shaft.

The transmission member 70 is connected to the needle holder 50 via theconnection pins 73 as shown in FIGS. 6 to 8 , so that when thetransmission member 70 moves along the hollow shaft 20 in the axialdirection, the needle holder 50 within the hollow shaft 20 movestogether with the transmission member 70 in the axial direction. Theconnection pins 73, in the embodiment four pins, extend radially throughthe slots 27 of the hollow shaft 20, respectively. The rear ends 73 b ofthe connection pins extend into a circumferential groove 72 formed inthe inner wall of the transmission member 70. Thus, when thetransmission member 70 advances along the threaded hollow shaft 20, therear ends 73 b of the connection pins 73 can rotate in the groove 72 ofthe transmission member 70. The pins 73 can be inserted through amounting hole 79 that extends through the transmission member into thegroove 72.

At an axial position between the rear end 70 b and the groove 72, aplurality, in the embodiment four, equidistantly arranged threadedthrough holes 74 are formed that serve for receiving mounting pins 75for mounting a needle position indication device in the form of a ringor sleeve 76 to the transmission member 70. The ring 76 hassubstantially the same axial length and an inner diameter that permitsmounting around the tube portion 64 of the actuator 60. The inner wallof the ring 76 is threadless, so that the ring 76 can slide along thetube portion 64. At positions corresponding to the threaded throughholes 74 in the transmission member 70, the ring 76 defines unthreadedholes 77 which permit only a threaded front portion 75 a of the mountingpins 75 to extend therethrough and engage the threaded holes 74 of thetransmission member 70. It shall be noted that the ring 76 is thinner inthe radial direction compared to the transmission member 70, since thering 76 has to fit into the space between the actuator and the handleportion in the radial direction. In the outer surface of the ring 76, acircumferential indication mark 78 is provided which may be, forexample, a groove, that may be provided with a coloring and/or a coloredring. Hence, when the transmission member 70 moves, the ring 76 with theindication mark 78 moves in the same way, for example, a same axialdistance. Therefore, the indication mark 78 is configured to display theaxial position of the needle holder 50, and therefore the axial positionof the tip 6 of the needle relative to the tip 3 of the bone anchor 1.For this purpose, there is a window in the handle portion 30, asexplained in greater detail below.

Turning now in addition to FIGS. 16 to 19 , the handle portion 30 willbe described in greater detail. The handle portion 30 may be anelongate, substantially cylindrical part that has a front end 30 a and arear end 30 b. An outer surface portion 31 that extends from a positionclose to the rear end 30 b to a distance from the front end 30 aincludes a gripping structure such as, for example, axial grooves.Between the outer surface portion 31 with the gripping structure and thefront end 30 a, the outer diameter of the handle portion may include atapered portion 33 that tapers and narrows towards the front end 30 a,so that the outer diameter of the handle portion 30 close to theactuator wheel 61 is smaller or has the same size as that of theactuator wheel 61. The handle portion 30 further defines an elongatepassage in the form of a cylindrical bore 32 extending from the frontend 30 a to a distance from the rear end 30 b. The diameter of the bore32 is such that, in the radial direction, the hollow shaft 20, theactuator tube 64, the transmission member 70 and the ring 76 can extendtherein.

Adjacent to the rear end 30 b, a cylindrical recess 34 with a bottom 34a is formed that is sized to receive a portion of the fixation member 40(see FIGS. 6 to 8 ). A coaxial opening 35 with a reduced inner diametercompared to the diameter of the bore 32 is provided in the bottom 34 aof the recess 34. The opening 35 has four rounded side recesses 35 aoffset from each other by 90° that are configured to receive the posts280 of the hollow shaft 20, in order to connect the hollow shaft 20 andthe handle portion 30 to each other in a rotationally secured manner.The posts 280 can pass through the side recesses 35 a, respectively, sothat free ends of the projections 280 project out therefrom.

In addition, a window 36 is provided in the handle portion 30 thatexposes a portion of the inside of the handle portion. Morespecifically, the window 36 exposes at least a portion of the ring 76with the marking 78. Thus, the marking 78 that is indicative of theposition of the needle holder 50 can be used for adjusting the positionof the needle holder 50, and thus the position of the needle 4. Thewindow 36 may have a rectangular shape with rounded edges, with a lengththat is greater than a difference between lengths of the longest and theshortest shanks of bone anchors that can be used, plus the length thatthe needle 4 is allowed to move. A groove 38 is formed in the wall ofthe handle portion 30 for receiving a shank length indication device inthe form of a slide 90 that is configured to indicate the possibletravel path of the needle holder 50 and which serves for setting a shanklength of the bone anchor that is actually being used. The groove 38 hasa substantially rectangular contour and a flat bottom. At the taperedportion 33 of the handle 30, the height of outer wall of the groovedecreases towards the front end 30 a, such that a portion of the bottomis free which permits the slide 90 to enter the groove 38 easily. Insidethe groove 38 there are protrusions 38 b along at least a portion of thelength of the window for cooperating with the slide 90. At the outerwall of the handle portion 30, around the window 36, are markings 39that are configured to indicate the length of the shank of the boneanchor that is being used. In the embodiment, the length is indicated inincrements wherein, for example, even numbers are indicated at one sideof the window and odd numbers are indicated at the opposite side of thewindow. For example, if the smallest length of a shank that can be usedis 35 mm and a greatest length of a shank that can be used is 60 mm, theeven numbers between 40 mm and 60 mm with an increment of 10 mm areindicated on one side of the window 36 and the odd numbers between 35 mmand 55 mm are indicated on the opposite side of the window. The markings39 are arranged such that the smallest length is displayed closer to therear end 30 b of the handle portion 30, and the displayed lengthsincrease towards the front end 30 a.

As shown in FIGS. 20 to 22 , the slide 90 includes a substantiallyrectangular flat plate that is configured to be slid into the groove 38and that can be moved therein in an axial direction, i.e., along alength axis of the plate that is parallel to the longitudinal axis ofthe handle portion 30. The slide 90 has a front end 90 a and a rear end90 b, wherein the front end is positioned closer to the actuator wheel61 in the assembled state when the slide 90 is in the groove 38. Alongitudinal slot 91 is formed in the middle of the slide in thetransverse direction which may extend almost along the whole length ofthe slide 90. The slot 91 is configured to display a portion of theactuator tube 64 and the ring 76 with the marking 78 that are visiblethrough the window 36 of the handle portion 30. Hence the slide alsoforms a needle position indication device. A countersink 92 around theslot 91 may improve the visibility of the ring 76 and may carrymarkings. On the upper side of the slide that faces outward, a pluralityof elongate gripping protrusions 93 may be formed that may be arrangedalong both long sides of slot 91 to allow gripping of the slide 90 andsliding of the slide in the groove 38.

On the surface of the countersink 92, markings are provided that can bealigned with the markings 39 on the handle portion 30 when the slide 90is moved. In greater detail, close to the rear end 90 b, a first type ofmarking 94 b may be provided that is configured to be aligned with oneof the markings 39 around the window 36 that indicate possible shanklengths. The first type of marking can be, for example, two arrowspointing to the center of the slot 91 in the circumferential directionof the handle portion 30, such that, when the slide 90 is at a positionin which the two arrows are aligned with a marking 39 on the handleportion 30, the marking 94 b indicates the length of a shank of aninserted bone anchor 1. This first type of marking 94 b may have acolor, for example, green. Moreover, a second type of marking 94 a maybe provided close to the front end 90 a of the slide 90. This secondtype of marking 94 a may indicate the maximum admissible projection ofthe needle 4 out of the shank 2. In other words, the second type ofmarking indicates the maximum admissible or desirable travel path of theneedle holder 50 to ensure the maximum admissible projection of theneedle. The marking 94 a may also include two arrows that point withtheir tips towards each other. A color of the second type of marking maybe red, for example, to indicate the limit of the admissible advancementof the needle 4. In between the first and the second type of markings,there may be a third type of marking 94 c that may include equidistantlyspaced apart dashes and/or dots on each side of the slot 91, wherein themarkings 94 c are offset from each other on one side relative to theother side. The markings 94 c may indicate the advancement of the needlein increments.

Generally, the markings 39 on the handle portion 30 provide a firstscale indicative of possible lengths of the shank of a bone anchor 1,while the markings on the slide 90 provide a second scale indicative ofthe possible positions of the tip 6 of the needle with respect to thetip of the bone anchor 1. Lastly, the slide 90 defines on each of thelong sides, at approximately the middle of the long sides, recesses, forexample, two V-shaped recesses 95 in the outer edge of the slide. Therecesses 95 are configured to cooperate with the protrusions 38 b insidethe groove 38. Thereby, the adjustment of the markings on the slide 90relative to the markings 39 on the handle portion 30 may be more easilyfacilitated, and the slide may be held at specific positions.

As further depicted in FIGS. 6 to 8 , the fixation member 40 fits atleast partially in the recess 34 at the rear end 30 b of the handleportion 30. The fixation member defines a threaded bore 43 that isconfigured to be screwed onto the posts 280 of the hollow shaft 20. Onthe side of the fixation member opposite the rear end 30 b of the handleportion 30, the fixation member defines a tool engagement recess 44 forscrewing the fixation member 40 onto the posts 280 of the hollow shaft20. The inner space between the posts 280 of the hollow shaft 20 is suchthat the needle holder 50 can extend therein and the threaded bore 43has a size such that insertion and/or removal of the needle 4 throughthe fixation member 40 is possible. The fixation member 40 is configuredto abut against the bottom 34 a of the recess 34 in the handle portion30 (FIGS. 7 and 8 ).

The parts and portions of the instrument and/or the bone anchorinsertion device, the bone anchor, and/or the needle may be made of anymaterial, preferably, however, of a bio-compatible material, such astitanium or stainless steel, or any other bio-compatible metal or metalalloy, or plastic material. For bio-compatible alloys, a NiTi-alloy, forexample Nitinol, may be used. Other materials that can be used are, forexample, Magnesium or Magnesium alloys, or bio-compatible plasticmaterials that can be used may be, for example, Polyether ether ketone(PEEK) or Poly-L-lactide acid (PLLA). The parts can be made of the sameor of different materials from one another. For the instrument, amaterial that is easy to clean may be preferred.

The needle holder 50, the hollow shaft 20, the transmission member 70with the ring 76, the handle portion 30 with the slide 90, and theactuator 60 are usually preassembled such that their respective frontends face in the direction of the connection portion 15. When the needleholder 50 is placed into the hollow shaft 20, the transmission member 70is screwed onto the hollow shaft 20 from the rear end thereof, and thepins 73 are inserted through the mounting hole 79, passed through theslots 27 of the hollow shaft 20 and screwed into the threaded holes 52of the needle holder 50. The actuator 60 is placed with the actuatorwheel 61 around the hollow shaft 20 and the set screws 601 aretightened. The ring 76 is mounted around the actuator tube 64 and fixedwith the mounting pins 75 to the transmission member 70, and theactuator tube 64 is mounted to the actuator wheel 61. After that, thehollow shaft 20 is fixed to the handle portion 30 via the fixationmember 40 that is screwed onto the threaded posts 280 of the hollowshaft 20. Tightening the fixation member 40 firmly fixes the hollowshaft 20 to the handle 30 so that rotation of the handle 30 also rotatesthe hollow shaft 20. The actuator 60 remains rotatable with respect tothe hollow shaft 20 and with respect to the handle portion 30.

To use the instrument 100 with a shank inserter 10, the optionalcoupling portion 15 is mounted to the connection portion 21 of thehollow shaft 20. The instrument 100 preassembled in this manner can beconnected to a shank inserter 10. To accomplish this, the connectionportion of the drive shaft is inserted into the connection portion 21 ofthe hollow shaft until the connection portion of the drive shaft isreceived in the receiving section 23, so that the form-fit engagementallows transmission of torque to the drive shaft. The shank inserter maybe already connected to a bone anchor 1 to be inserted into bone, or thebone anchor 1 can be fixed to the shank inserter 10 when the shankinserter has already been connected to the instrument 100.

In operation, when the actuator wheel 61 is rotated, the rotationalmovement of the actuator tube 64 forces the transmission member 70 totravel in an axial direction via the engagement of the thread 71 of thetransmission member 70 with the thread 200 of the hollow shaft 20. Sincethe transmission member 70 is connected via the pins 73 to the needleholder 50, the needle holder 50 will travel axially together with thetransmission member 70.

The needle 4 can be inserted and removed by means of a push and turnaction as follows. When the projections 8 a are received in the endportions 59, the needle 4 is secured against inadvertent removal fromthe needle holder 50. When the shoulder 7 a of the holding portion ofthe needle 4 abuts against the washer 57, the spring 55 urges the washeragainst the shoulder 7 a, so that the needle 4 as a whole is biasedtowards the rear end 50 b of the needle holder 50. Thereby, theprojections 8 a are held in the transverse end portions 59 of the axialrecesses 58. Removal of the needle 4 is effected by pushing the holdingportion of the needle against the washer 57, which frees the projections8 a so that they can be moved out of the transverse end portions 59 byrotating the needle in a counter or opposite direction compared to whenthe needle is attached to the needle holder. For example, in theembodiment, the end portions 59 extend in the counterclockwise directionwhen viewed from the read end 50 b, so that pushing and rotating theneedle in the counterclockwise direction locks the needle 4 in theneedle holder 50, while pushing and rotating the needle in the clockwisedirection releases the needle 4 from the needle holder 50. This push andturn action allows for a quick and simple mounting and removal of theneedle. The rod portion 5 of the needle may be exchanged relative to theholding portion, or the entire rod portion together with the holdingportion of the needle 4 can be replaced or exchanged.

Referring to FIGS. 23 a to 23 d , in clinical use, once a bone anchorwith a specific shank length has been selected, the slide 90 is adjustedto the position in which its first type marking 94 b is aligned with themarking 39 which corresponds to the shank length of the bone anchor. Inthe example shown, a bone anchor with a shank length of 60 mm has beenselected, and the slide 90 has been adjusted correspondingly.

Once the needle 4 has been inserted and locked in the needle holder 50,the position of the needle is adjusted with the actuator. By rotatingthe actuator wheel 61, for example, in the clockwise direction, theneedle 4 is advanced, and by rotating the actuator wheel, in thisexample, in the counterclockwise direction, the needle is retracted.During adjustment of the position of the needle 4, the marking 78 on thering 76 displayed through the window 36 and the slot 91 indicates theposition of the tip 6 of the needle 4 relative to the tip 3 of the boneanchor 1.

As shown in FIG. 23 a , the surgical instrument prepared in this manneris ready to insert the bone anchor 1 into bone, in the example, in apedicle of a vertebra 500. Next, as shown in FIG. 23 b , the bone anchoris placed onto the bone surface and the tip 6 of the needle 4 is hit orotherwise advanced into the bone until the needle 4 has penetrated thecortical bone.

Next, as depicted in FIG. 23 c , the handle portion 30 is heldstationary and the actuator wheel 61 is rotated in the clockwisedirection. Thereby, the needle 4 penetrates deeper into the bone. Thedistance of travel of the tip 6 of the needle can be seen by theposition of the marking 78 of the ring 76 relative to the first typemarking 94 b.

As further shown in FIG. 23 d , once the desired depth has been reached,the actuator wheel 61 of the actuator 60 is held stationary and thehandle portion 30 is rotated in the clockwise direction to screw thebone anchor 1 over the needle 4 into the bone. Preferably, the boneanchor 1 is a self-tapping bone anchor that is configured to cut thethread into the bone by itself during rotation.

Finally, the shank inserter 10 can be decoupled from the bone anchor 1together with the instrument 100 still attached to the shank inserterand with the needle 4 still extending through the entire device.Alternatively, the needle 4 can be removed first, and the shank inserter10 can then be released from the bone anchor thereafter.

Since the path the needle can travel covers about a length of the shankof a usual bone anchor or more, the instrument 100 and the same needle 4can be used in connection with different bone anchors having differentlengths. The needle position can be monitored during use as it isdisplayed on the slide 90.

Referring to FIG. 24 , a second embodiment of the surgical instrument isshown. Identical or similar parts and portions are indicated with thesame reference numerals, and the descriptions thereof will not berepeated. The shank inserter 10 and the instrument 100 are identical tothe previous embodiment. However, between the shank inserter 10 and theinstrument 100, an adapter 1000 is mounted that has a rear end that iscoupled to the hollow shaft 20 in the same manner as the drive shaft ofthe previous embodiment is coupled to the hollow shaft 20. The adapter1000 has a front connection portion that is connected to the shankinserter 10. The hollow shaft 20 of the instrument 100 is coupled to aninner shaft (not shown) of the adapter member 1000, which is alsocoupled to the drive shaft of the shank inserter 10. Thus, torque can betransmitted from the handle portion 30 through the adapter member 1000to the drive shaft of the shank inserter 10. A secondary instrument1010, such as a navigation array for optical or any other navigation,can be mounted on the adapter member 1000 via a mounting sleeve 1001.The mounting sleeve 1001 may be, for example, rotatable around the shaftof the adapter member 1000. By means of this, while the torque istransmitted via the handle 30 to the drive shaft, the secondaryinstrument 1010 can be kept stationary by gripping the secondaryinstrument 1010 or the mounting sleeve 1001 with the other hand.Thereby, the orientation of the secondary instrument 1010 such as anavigation array can be maintained relative to the rest of the device,e.g., while the rest of the device is rotated. This may be used forsurgery under fluoroscopy or with computer-based navigation assistedsystems.

It shall be noted that instead of a navigation array, other secondaryinstruments can also be used via the adapter member 1000.

Referring to FIGS. 25 to 27 , a further embodiment of the needle holderand the needle is explained. Parts and portions that are identical orsimilar to the previous embodiments are indicated with the samereference numerals, and the descriptions thereof will not be repeated.The needle 4′ is connectable to the needle holder 50′ via a threadedconnection. For this purpose, the holding portion of the needle 4′ has,between a cylindrical front portion 7′ in which the rod portion 5 issupported and a rearward head portion 9′, an intermediate threadedportion 8′ with an external thread 81. The outer diameter of thethreaded portion 8′ may be greater than that of the cylindrical frontportion 7′ and smaller than that of the head portion 9′.

The needle holder 50′ is cylindrical, similar to the previousembodiment, and defines a coaxial channel for passing through the rodportion 5 of the needle 4′ and for receiving at least part of theholding portion of the needle. A front portion 51′ of the channel isconfigured to receive the cylindrical front portion 7′ of the needle. Arear portion 53′ of the channel has an internal thread 53 a′ that isconfigured to cooperate with the external thread 81 of the holdingportion of the needle. The rear portion 53′ may be located between theholes 52 for the pins 73 and the rear end 50 b. At the transitionbetween the front portion 51′ and the rear portion 53′ of the channel, astep 51 a′ may be formed that may serve as an abutment to limit theinsertion of the needle into the needle holder 50′. Moreover, when theneedle 4′ is screwed into the needle holder 50′, the needle 4′ can betightened against the abutment. This may result in a stronger and saferconnection. Between the rear end 50 b and the rear portion 53′, acoaxial bore 53 b′ may be formed, and the head portion 9′ may abutagainst the rear end 50 b. The needle holder 50′ may be used in theinstrument instead of the needle holder 50.

In use, when the needle holder 50′ is inserted into the hollow shaft 20,the needle 4′ can be removed and/or exchanged by means of screwing theneedle into and out of the needle holder. Preferably the needle holder50′ is in the rearmost position when the needle 4′ is mounted orexchanged. The threaded connection simplifies the handling of the needleand allows for a quicker exchange of the needle.

Further modifications of the instrument or the parts thereof may bepossible. In particular, the shapes of the various parts are not limitedto the specific shapes shown in the embodiments. The instrument can alsobe used, for example, for inserting a syringe for injecting bone cementor other substances after or instead of a needle as shown in theembodiment. For the actuating mechanism, any suitable actuatingmechanism that can convert a rotational motion of an actuator into atranslational motion of the needle holder can be used. The instrumentcan also be used in connection with, for example, a drill instead of ashank inserter, or with other suitable surgical instruments. Theinstrument can also be used without a needle or with needles ofdifferent types and lengths.

While the present invention has been described in connection withcertain exemplary embodiments, it is to be understood that the inventionis not limited to the disclosed embodiments, but is instead intended tocover various modifications and equivalent arrangements included withinthe spirit and scope of the appended claims, and equivalents thereof.

What is claimed is:
 1. An instrument for use in surgery, the instrumentbeing connectable to a bone anchor insertion device that comprises adrive shaft configured to engage a bone anchor, the drive shaft defininga coaxial channel for receiving a needle therethrough, the instrumentcomprising: a hollow shaft connectable to the drive shaft in arotationally fixed manner; a needle holder configured to hold a needleand movable axially relative to the hollow shaft; an actuator rotatablerelative to the hollow shaft; and a transmission member connectable tothe needle holder and movable axially relative to the actuator, whereinthe transmission member is positionable around at least part of thehollow shaft and comprises a first advancement surface engageable with asecond advancement surface of the hollow shaft to convert rotationalmovement of the actuator into axial movement of the needle holderrelative to the hollow shaft for axially advancing and retracting theneedle held by the needle holder relative to the hollow shaft.
 2. Theinstrument of claim 1, wherein the needle holder is positionable atleast partially within the hollow shaft and is movable along alongitudinal axis of the hollow shaft.
 3. The instrument of claim 1,wherein the transmission member comprises a sleeve-like portion that ispositionable at least partially around the hollow shaft.
 4. Theinstrument of claim 1, wherein the transmission member comprises atleast one engagement member that is configured to extend through arecess in the hollow shaft to engage the needle holder.
 5. Theinstrument of claim 1, wherein the first advancement surface is providedat an inner surface of the transmission member and the secondadvancement surface is provided at an outer surface of the hollow shaft.6. The instrument of claim 1, wherein the first advancement surface andthe second advancement surface each comprises a thread.
 7. Theinstrument of claim 1, wherein the actuator comprises an actuator wheelpositionable at least partially around the hollow shaft and a guidingstructure for guiding the transmission member when the actuator isrotated relative to the hollow shaft.
 8. The instrument of claim 7,wherein the actuator wheel and the hollow shaft are connected in amanner such that when the actuator wheel is rotated, the actuator wheelis configured to be held at defined rotational increments relative tothe hollow shaft.
 9. The instrument of claim 1, further comprising ahandle portion connectable to the hollow shaft to transmit torque to thehollow shaft.
 10. The instrument of claim 9, wherein the handle portiondefines an elongate passage into which the hollow shaft is configured toextend.
 11. The instrument of claim 10, wherein a portion of theactuator is configured to extend into the elongate passage of the handleportion.
 12. The instrument of claim 9, further comprising a fixationmember configured to fixedly connect the hollow shaft to the handleportion.
 13. The instrument of claim 1, further comprising a needleposition indication device configured to indicate an axial position ofan inserted needle with respect to a shank of a bone anchor.
 14. Theinstrument of claim 1, further comprising a length indication deviceconfigured to indicate a length of a selected bone anchor, wherein thelength indication device is adjustable to accommodate bone anchors withdifferent lengths.
 15. The instrument of claim 1, wherein the hollowshaft comprises an end portion that is releasably connectable to an endportion of the drive shaft.
 16. The instrument of claim 15, wherein theend portion of the hollow shaft comprises a standard coupling.
 17. Theinstrument of claim 1, wherein the needle holder is configured toreleasably receive the needle without disassembling the instrument. 18.A method of implanting a bone anchor into bone with a surgicalinstrument comprising a bone anchor insertion device that comprises adrive shaft configured to engage the bone anchor, the drive shaftdefining a coaxial channel for receiving a needle therethrough, and aninstrument comprising a hollow shaft connectable to the drive shaft in arotationally fixed manner, a needle holder configured to hold a needleand movable axially relative to the hollow shaft, an actuator rotatablerelative to the hollow shaft, and a transmission member connectable tothe needle holder and movable axially relative to the actuator, whereinthe transmission member is positionable around at least part of thehollow shaft and comprises a first advancement surface engageable with asecond advancement surface of the hollow shaft to convert rotationalmovement of the actuator into axial movement of the needle holderrelative to the hollow shaft for axially advancing and retracting theneedle held by the needle holder relative to the hollow shaft, themethod comprising: advancing a bone anchor to the bone while the boneanchor is engaged by the bone anchor insertion device and the boneanchor insertion device is connected to the instrument and when a needleis held by the needle holder and extends distally past a tip of the boneanchor; rotating the actuator while holding a rotational orientation ofthe hollow shaft to advance the needle into the bone while maintainingan axial position of the bone anchor; rotating the hollow shaft whileholding a rotational orientation of the actuator to advance the boneanchor over the needle into the bone while maintaining an axial positionof the needle; detaching the bone anchor insertion device and the needlefrom the bone anchor.
 19. The method of claim 18, wherein a held needleis removable from or adjustable relative to the needle holder withoutdisassembling any other portion of the instrument.
 20. An instrument foruse in surgery, the instrument being connectable to a bone anchorinsertion device that comprises a drive shaft configured to engage abone anchor, the drive shaft defining a coaxial channel for receiving aneedle therethrough, the instrument comprising: a hollow shaftconnectable to the drive shaft in a rotationally fixed manner; a needleholder configured to hold a needle and movable axially relative to thehollow shaft; an actuator rotatable relative to the hollow shaft; atransmission member connectable to the needle holder and movable axiallyrelative to the actuator, the transmission member comprising a firstadvancement surface engageable with a second advancement surface of thehollow shaft to convert rotational movement of the actuator into axialmovement of the needle holder relative to the hollow shaft for axiallyadvancing and retracting the needle held by the needle holder relativeto the hollow shaft; and a closed ring configured to extend entirelyaround at least part of the actuator, wherein the closed ring is fixedlyconnected to and movable together with the transmission member relativeto the actuator.